Fighting deadly flab: Half a million cancers a year caused by obesity – WHO

Obesity and being overweight are to blame for at least half a million cases of cancer a year, says the World Health Organization's cancer research agency. Women are especially at risk, and the problem is most serious in North America.

High body mass index (BMI) has become a major cancer risk factor,
responsible for 3.6 percent, or 481,000 of new cancer cases in
2012. The WHO's International Agency for Research on Cancer
(IARC) published its study in the The Lancet
Oncology journal on Wednesday.

The researchers used data from the GLOBOCAN database of cancer
incidence and mortality for 184 countries in 2012 to create a
model that could estimate the number of cancers caused by
obesity. These include cancers of the oesophagus, colon, rectum,
kidney, pancreas, gallbladder, postmenopausal breast, ovary and
endometrium.

The scientists relied on BMI as a measure, which is calculated as
a person's weight in kilograms divided by the square of their
height in meters. A body mass index of 25 is considered to be
overweight, while obesity starts at 30 on the index.

"The number of cancers linked to obesity and overweight is
expected to rise globally along with economic development,"
Christopher Wild, IARC's director said.

According to the study, it is vital for a person to remain fit
and maintain a healthy weight, which will reduce the risk of
developing a wide range of cancers. The problem is most acute in
developed countries.

“These findings emphasize the need for a global effort to
abate the increasing numbers of people with high BMI,” the
researchers said. “Assuming that the association between high
BMI and cancer is causal, the continuation of current patterns of
population weight gain will lead to continuing increases in the
future burden of cancer.”

Highest obesity-related cancer rate in US

The study revealed the geography behind cancer and fat to be
interesting. It was not only economy dependent, but also
corresponded to the human development index (HDI).

At the moment, North America leads the ratings with the worst
cancer problem linked to weight. That is, almost a quarter of
global cancer cases associated with high BMI, or 111,000
obesity-related cancers diagnosed in 2012.

Europe has around 6.5 percent of all new cancers a year – or
approximately 65,000 cases.

Most of the Asian countries have a smaller proportion of
fat-related cancers. However, big populations turn a tiny
percentage into tens of thousands of cases.

IARC drew the example of China, where just 1.6 percent of cancers
leads to a mortality rate of 50,000.

In Africa, not surprisingly, obesity accounted for a tiny 1.5
percent of cancer cases in 2012, with sub-Saharan Africa
contributing the least.

The second striking feature is that women are
“disproportionately affected” by cancers, related to
overweight. Melina Arnold, who co-led the IARC study, explained
this trend with endometrial (womb/uterus) and post-menopausal
breast cancers.

In males, excess weight was responsible for 1.9 percent or
136,000 new cancers, and in females it was 5.4 percent or 345,000
new cases.

"Our findings add support for a global effort to address the
rising trends in obesity. The global prevalence of obesity in
adults has doubled since 1980,” Arnold said.

“If this trend continues it will certainly boost the future
burden of cancer, particularly in South America and North Africa,
where the largest increases in the rate of obesity have been seen
over the last 30 years," the study’s leader added.